WO1995023291A1

WO1995023291A1 - Pressure oil supply device

Info

Publication number: WO1995023291A1
Application number: PCT/JP1995/000287
Authority: WO
Inventors: Toshiro Takano; Mitsumasa Akashi; Yoshio HOSHINO
Original assignee: Komatsu Ltd.
Priority date: 1994-02-24
Filing date: 1995-02-24
Publication date: 1995-08-31
Also published as: JPH07286602A; JP3511414B2

Abstract

A pressure oil supply device comprises a variable capacity type hydraulic pump, of which discharge amount is controlled by a load pressure of a load pressure detecting circuit, a pressure compensating valve composed of a check valve portion and a pressure reducing valve portion, and a directional control valve for supplying a pump discharge pressure oil to an actuator. The check valve portion comprises a spool for providing communication and shut-off between a pump discharge circuit of the variable capacity type hydraulic pump and a pump port of the directional control valve, and the pressure reducing valve portion comprises a spool which is adapted to be pushed toward a first position where it is assisted by the load pressure of the actuator to provide communication between the pump discharge circuit and the load pressure detecting circuit, and to be pushed toward a second position where it is assisted by a weak spring and the load pressure of the load pressure detecting circuit to provide shut-off between the pump discharge circuit and the load pressure detecting circuit and to push the spool of the check valve portion in a closing direction and which is adapted to be slowly moved from the second position to the first position and has a bleed-off circuit for bleeding a part of pressure oil from the pump discharge circuit at an intermediate position between the second position and the first position to a tank.

Description

Description Pressure oil supply device Technical field

TECHNICAL FIELD The present invention relates to a pressure oil supply device that supplies discharge pressure oil of a variable displacement hydraulic pump to a factory.

Background art

As a conventional pressure oil supply device of this kind, for example, a pressure oil supply device disclosed in Japanese Patent Application No. 4-161920 is known.

As shown in Fig. 1, this includes a variable displacement hydraulic pump 1 (hereinafter referred to as a variable hydraulic pump 1), a pressure compensating valve 4 comprising a tick valve section 2 and a pressure reducing valve section 3, and a directional control valve 5 as shown in FIG. To supply pressurized oil to the factory. The check valve section 2 has a spool 9 that communicates and shuts off between the ports 7 and 8 by a pressure difference between the inlet port 7 and the outlet port 8. The pressure reducing valve section 3 is pushed by the pressure of the first pressure chamber 10 in a direction to connect the first port 13 and the second port 14, and the pressure of the second pressure chamber 11. 12 has a spool 15 which is pushed in a direction to shut off the first port 13 and the second port 14. Direction control valve 5 Soot that can be slid by the pilot pressure. And the first and second load pressure detecting ports between the pump port 16 and the first and second load pressure detecting ports 17 and 18 by the spool 23. Between ports 17 and 18 and ports 1 and 2 for the first and second actuaries, and between ports 19 and 20 for the first and second Communication and cutoff between ports 19 and 20 and first and second tank ports 21 and 22.

The pump discharge passage 24 of the variable hydraulic pump 1 communicates with the inlet port 7 and the first port 13. A pump adjusting directional control valve 26 for controlling the displacement by tilting the swash plate 25 of the variable hydraulic pump 1 is connected to a second port 14 via a load pressure detecting path 27. The outlet port 8 of the check valve section 2 communicates with the pump port 16. The first pressure chamber 10 of the pressure reducing valve section 3 communicates with the first and second load pressure detection ports 17, 18, and the second pressure chamber 11 communicates with the second port via the throttle 28. It communicates with 14. In the pressure reducing valve section 3, the free chamber 30 is inserted into the blind hole 29 of the spool 15 to form a pressure chamber 31. The pressure chamber 31 is connected to the pressure chamber 31 through the damper throttle 32. It is in communication with the slit-shaped opening 33.

In such a pressure oil supply device, when the spool 23 of the directional control valve 5 is in the neutral position shown in the figure, the spool 15 of the pressure reducing valve section 3 is pushed to the left by the weak spring 12 to check the valve. Pushing spool 9 of part 2 in the closing direction.

On the other hand, the pump discharge pressure is increased by a predetermined differential pressure, for example, 20 kg / cm ² , from the pressure of the load pressure detection path 27 by the directional control valve 26 for pump adjustment. When 23 is in the neutral position, the pressure in the load pressure detection path 27 is zero, so the pump discharge pressure is 20 kg / cm ² .

Then, the spool 9 of the check valve section 2 is pushed rightward by the pressure of the inlet port 7 to open the space between the inlet port 7 and the outlet port 8, and the outlet port 9 is opened. When the pressure of the gate 8 reaches 20 kg / cm2, it is pushed to the left to close between the ports 7 and 8. The spool 23 of the directional control valve 5 is moved from the state shown in FIG. 1 in the direction of the arrow, and the pump port 16 is moved to the second load pressure detection port 18 and the first load pressure detection port 17 is moved to the first position. When the first hydraulic oil supply position is connected to the first actuator 19 and the second actuator port 20 is connected to the second tank 22, the discharge pressure oil of the variable hydraulic pump 1 is Supplied to the factory overnight 6, the pressure in the factory 6 rises to a pressure corresponding to the external load.

The pressure in the actuator 6, that is, the load pressure, flows into the first pressure chamber 10, pushes the spool 15 to the right and presses the first port 13 and the second port 1 at the small diameter portion 33. 4 through which the pump discharge pressure flows into the second pressure chamber 11 via the first port 13, the small-diameter portion 33, the second port 14, and the throttle 28, and the spool discharges. 15 is pushed in the direction to shut off the first port 13 and the second port 14, and at the same time, the load pressure is introduced into the load pressure detection path 27, and the discharge amount of the variable hydraulic pump 1 increases. . That is, the pressure reducing valve section 3 pushes the spool 15 to the right until the pressure in the first pressure chamber 10 and the pressure in the second pressure chamber 11 become equal, and the pump discharge path 24 and the second pressure chamber 1 1 When the pressures in the first and second pressure chambers 10 and 11 become equal, the spool 15 is pushed to the left by the weak spring 1 2 to close the pump discharge path 24 and the second pressure chamber 11. At the same time, contact the check valve part 2. As a result, the pressure in the load pressure detection path 27 becomes equal to the pressure in the first pressure chamber 10, that is, the load pressure, and the pump discharge pressure is changed by the pump control directional control valve 26. The pressure is controlled to be higher than the pressure in the load pressure detection path 27 by a certain differential pressure (here, 20 kg / cm ² ). Since this pump discharge pressure is guided to the pump port 16 via the check valve section 2, the direction control is performed. A differential pressure (= 20 kg / cm ² ;) is maintained between the inlet pressure and the outlet pressure ′ (= load pressure) of the valve 5. Therefore, the directional control valve 5 The flow supplied to the actuator 6 is controlled only by the change in the opening area between the inlet side and the outlet side due to the movement of the spool 23 of FIG.

In the above operation, when the spool 15 moves to the right due to the load pressure in the first pressure chamber 10, the pressure oil in the pressure chamber 31 passes through the damper throttle 3 2 and the first port 13 Side, the spool 15 moves slowly to the right according to the speed of the flow of the pressurized oil.

Therefore, when the spool 23 of the directional control valve 5 is moved rightward to the first hydraulic oil supply position, the first port 13 and the second port 14 gradually communicate with each other, and the load pressure is reduced. Since the pressure in the detection path 27 gradually increases, the discharge amount of the variable hydraulic pump 1 gradually increases, and the actuator 6 operates slowly.

If the pressure chamber 3 1 and the damper throttle 3 2 are not provided in the spool 15 of the pressure reducing valve section 3, the spool 15 will suddenly move to the right and the pressure in the load pressure detection path 27 will suddenly increase. And the discharge amount of the variable hydraulic pump 1 sharply increases, so that the actuator 6 operates suddenly.

In the case of the above-described pressure oil supply device, the actuator 6 is slowly operated when the spool 23 of the directional control valve 5 is moved from the neutral position to the pressure oil supply position. It is suitable for performing an inching operation (fine operation) of the actuator 6 because it can be operated.

That is, when the spool 23 of the directional control valve 5 is moved a small distance from the neutral position toward the pressure oil supply position to reduce the meter-in opening area, that is, Supplying a small amount of pressurized oil 6 When inching operation, for example, when pressurizing oil is supplied to the hydraulic motor for turning the hydraulic shovel to position the upper body at a predetermined position and stop, or when raising the boom during skidding In this case, the smaller the change in the flow rate of the supply flow to the actuator 6 with respect to the change in the increase in the metering opening area of the directional control valve 5, the easier these operations are. Desirable to do.

However, with the above-described structure of the pressure oil supply device, it is true that the spool 15 constituting the pressure reducing valve portion 3 of the pressure compensating valve 4 moves slowly to the right, and as a result, the variable hydraulic pump The discharge rate of 1 gradually increases;: From,, the operability is slightly improved at the beginning of the inching operation, but it can be changed with the spool 23 of the directional control valve 5 moved a small distance. The discharge amount of the hydraulic pump 1 becomes a value commensurate with the load pressure over time, and the flow rate required by the meter opening area of the directional control valve 5 is supplied to the actuator over time. After a short period of time elapses after the inching operation, the movement of the actuate will become faster, and the inching operability will be poor.

In other words, even if the above-mentioned rightward movement of the spool 15 of the pressure reducing valve section 3 is slow, the first port 13 and the second port 14 communicate with each other after a certain period of time. Since the same pressure as the load pressure applied to the first pressure chamber 10 is output to the load pressure detection path 27, the discharge amount of the variable hydraulic pump 1 becomes a flow rate commensurate with the load pressure. A slight amount of time elapses when the actuating unit 6 is inching-operated by supplying a flow proportional to the area of the mesh opening by the spool 23 of the directional control valve 5 to the unit 6. Doing so will increase the speed of the work, so it will be difficult to perform the necessary work in the inching operation. When the spool 23 is moved a large distance from the neutral position to the pressure oil supply position to increase the meter-in opening area, a large amount of pressure oil When supplying oil, the slight variation does not matter at all because the amount of pressurized oil supply is large.

The present invention has been made in order to improve such a problem, and has as its object to provide a pressure oil supply device in which operability is improved throughout the entire operation of an inching operation. That is what you do. Disclosure of the invention

In order to achieve the above object, according to one aspect of the present invention, there is provided a variable displacement hydraulic pump in which a discharge amount is controlled by a load pressure of a load pressure detection path, and a check valve unit. A pressure compensating valve comprising a pressure-reducing valve and a direction control valve for supplying pump discharge pressure oil to the actuator. The tucking valve comprises a pump discharge passage for the variable displacement hydraulic pump. A spool that communicates with and shuts off the pump from the directional control valve;

The pressure reducing valve section,

The pump pressure is pushed toward the first position that connects the pump discharge path and the load pressure detection path by the load pressure of the actuator, and the load is pressed by the weak spring and the load pressure of the load pressure detection path. A spool that is pressed toward a second position that blocks a pump discharge path and the load pressure detection path and that pushes a spool of the check valve unit in a closing direction, and the spool is a second spool. To move slowly from the position to the first position,

Hydraulic oil from the pump discharge passage at an intermediate position between the second position and the first position A pressurized oil supply device is provided which has a bleed-off circuit that allows a part of the oil to flow into the tank.

According to the above configuration, when the spool of the directional control valve is moved from the neutral position to the pressure oil supply position and the pump discharge pressure oil is supplied to the actuator, the pump pressure is reduced by the load pressure of the actuator. As the spool of the pressure reducing valve moves slowly toward the first position, the pressure in the load pressure detection path rises slowly, and the discharge volume of the variable displacement hydraulic pump decreases. It has increased significantly, and there has been no sudden operation of Actuyue.

Also, when the spool of the pressure reducing valve section is located at an intermediate position between the second position and the first position, a part of the pump discharge pressure oil flows out to the tank, and the pressure in the load pressure detection path becomes lower than the load pressure. Therefore, the discharge volume of the variable displacement hydraulic pump is smaller than the value corresponding to the load pressure, and the supply flow rate to the actuator is the required flow rate due to the opening area of the directional control valve. When the spool moves to the first position, the pressure in the load pressure detection path becomes equal to the load pressure, and the discharge amount of the variable displacement hydraulic pump becomes a value that matches the load pressure. As a result, the supply flow rate to the factory is the required flow rate due to the area of the directional control valve opening.

Therefore, when the directional control valve is operated by a very small amount to perform the inching operation of the actuator, the starting speed of the actuator becomes slower, so that a smooth inching operation can be performed. However, when the actuator is moved to the first position, the supply flow to the actuator can be operated at a predetermined speed because the flow rate supplied to the actuator becomes the required flow rate based on the opening area of the directional control valve.

In the above configuration,

The pressure reducing valve section receives the load pressure and moves the spool to the first position. A first pressure chamber that pushes toward the pump, a pressure chamber that communicates with the pump discharge path through a damper throttle, and pushes the spool toward the second position, and a throttle that connects to the load pressure detection path. And a second pressure chamber which communicates and presses the spool toward the second position. When the spool is at the second position, the pressure chamber and the load pressure detection path are shut off. When the spool is at an intermediate position between the second position and the first position, the pressure chamber communicates with the tank and the load pressure detection path, and when the spool is at the first position, the pressure chamber is connected to the load pressure. It is desirable to adopt a configuration that communicates with the detection path.

According to another aspect of the present invention, there is provided

A variable displacement hydraulic pump whose discharge amount is controlled by the load pressure in the load pressure detection path;

A directional control valve that is switched from the neutral position to the pressurized oil supply position by an operation finger and supplies pump discharge pressure oil to the actuator all the time, and the meteine opening area is proportional to the operation finger. When,

A pressure compensating valve which is pushed in the opening direction by the pump discharge pressure and is pushed in the closing direction by the load pressure of the actuator to make the primary pressure correspond to the load pressure;

A blade-off circuit connected to the load pressure detection path;

It is provided in the bleed-off circuit. When the magnitude of the operation command is an intermediate value, the bleed-off circuit is at the bleed-off position. And a pressure oil feed-off device comprising:

According to the above configuration, The main opening area of the directional control valve and the load pressure bleed-off valve are switched according to the size of the operation finger, and when the magnitude of the operation command to be performed for inching is set to an intermediate size, the Since the opening area is small and the load pressure blade-off valve is at the blade-off position, the discharge amount of the variable displacement hydraulic pump during the inching operation is less than the required flow rate, and the operation is interrupted. It works as a unit and improves the inching operability.

In the above configuration,

The operation finger is a pilot pressure output from the hydraulic pilot valve as a pressure proportional to the operation amount of the operation lever,

The directional control valve is switched from the neutral position to the pressurized oil supply position by the pilot port pressure and supplies the pump discharge pressure oil to the actuator all the time, and its meter-in opening area is equal to the pilot pressure. Preferably it is proportional to pressure.

In the above configuration,

The directional control valve has a spool fitted in the valve body and slidably moved between a neutral position and a pressure oil supply device by a spring and a pilot pressure in a pressure receiving chamber. hand,

A plurality of the directional control valves are overlapped and connected to each other,

Oil holes connected between the valve bodies adjacent to the valve bodies and check valves communicating the oil holes with the pressure receiving chamber are provided, and the oil holes are provided by the load pressure blow-off valve. It is preferable to connect to the pressure receiving part.

Further, in the above configuration,

The pressure compensating valve comprises a check valve section and a pressure reducing valve section; The check valve unit has a spool that communicates and shuts off a pump discharge path of a variable displacement hydraulic pump and a pump port of a directional control valve.

The pump pressure is pressed toward the first position that connects the pump discharge path and the load pressure detection path by the load pressure of the actuator, and the pump discharge path and the load pressure detection are performed by the weak spring and the load pressure of the load pressure detection path. And a spool that is pressed toward a second position that blocks the passage from the road and pushes the spool of the check valve portion in a closing direction, and the spool moves from the second position to the first position. It is preferable to move slowly toward it. BRIEF DESCRIPTION OF THE FIGURES

The invention will be better understood from the following detailed description and the accompanying drawings illustrating an embodiment of the invention. The embodiments shown in the accompanying drawings are not intended to specify the invention, but merely to facilitate explanation and understanding.

In the figure,

FIG. 1 is a cross-sectional view of a conventional pressure oil supply device.

FIG. 2 is a sectional view of a first embodiment of the pressure oil supply device according to the present invention.

FIG. 3 is a cross-sectional view for detailed description of the pressure reducing valve section of the first embodiment.

FIG. 4 is a cross-sectional view for explaining the operation of the pressure reducing valve section of the first embodiment.

FIG. 5 is a cross-sectional view for explaining the operation of the pressure reducing valve section of the first embodiment. It is.

FIG. 6 is a sectional view of a second embodiment of the pressure oil supply device according to the present invention.

FIG. 7 is a chart showing the relationship between the operation amount of the operation lever of the second embodiment and the pilot pressure.

FIG. 8 is a sectional view showing another example of the pressure compensating valve of the second embodiment.

FIG. 9 is a schematic diagram showing still another example of the pressure compensating valve of the second embodiment.

FIG. 10 is a plan view of an example in which a plurality of directional control valves are superimposed as an application example of the second embodiment.

FIG. 11 is a sectional view taken along the line XI—XI of FIG.

FIG. 12 is a cross-sectional view taken along the line X-X in FIG.

FIG. 13 is a cross-sectional view showing a structure of a directional control valve for supplying pressure oil to a factory which does not need to be inked in the application example.

FIG. 14 is a schematic diagram showing another configuration for operating the directional control valve.

FIG. 15 is a schematic diagram showing still another configuration for operating the directional control valve. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a pressure oil supply device according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

A first embodiment of the present invention will be described with reference to FIGS. Note that The same members as those in the related art are denoted by the same reference numerals, and detailed description is omitted. In the pressure reducing valve section 3 of this embodiment, third 'fourth ports 40, 41 are formed between the first port 13 and the second port 14, and the third port 40 is formed. A small-diameter portion 43 is formed in the spool 15 to communicate with the tank 42 and to communicate and block the third port 41 and the second port 14.

As shown in FIG. 3, the free piston 30 has a small diameter portion 44 and an oil hole 45 communicating the small diameter portion 44 with the pressure chamber 31. The spool 15 has a port 46 for connecting and blocking the small diameter portion 44 to the third port 40, and has a blind hole 29 of the spool 15 and a free piston. A port 48 connecting the small diameter portion 43 to the space portion 47 between the small diameter portion 44 of 30 is formed. Further, the second port 14 and the second pressure chamber 11 are always in communication with each other by a gap (throttle) between the spool insertion hole 49 and the spool 15.

Next, the operation of the present embodiment will be described.

When the spool 23 of the directional control valve 5 is in the neutral position as shown in Fig. 2

As shown in FIG. 3, the pump discharge passage 24 includes a first port 13, a small-diameter portion 33, a damper throttle 32, a pressure chamber 31, an oil hole 45, a space 47, and a port 47. Port 48 communicates with the fourth port 41, the fourth port 41 is cut off from the second port 14, the port 46 communicates with the first port 13 and has a space. 4 It is cut off from 7.

That is, the pump discharge passage 24 communicates with the pressure chamber 31 through the damper throttle 32, and the pressure chamber 31 is isolated from the second port 14.

When the spool 23 of the directional control valve 5 is slightly moved to the right from the position shown in Fig. 2. The spool 15 of the pressure reducing valve 3 is pushed rightward by the load pressure acting on the first pressure chamber 10 and takes a position where it balances on the way as shown in FIG.

As a result, since the fourth port 41 communicates with the second port 14, the pump discharge passage 24 has the first port 13, the small-diameter portion 33, and the damper damper.

3 2, pressure chamber 31, oil hole 45, space 47, port 48, small diameter part

4 3, the second port 14 is communicated, and at the same time, the space portion 47 communicates with the third port 40 from the port 46.

Because of this, a part of the pump discharge pressure flows to the tank 42. The load pressure acting on the load pressure detection path 27 is lower than the load pressure acting on the first pressure chamber 10. As a result, the discharge amount of the variable hydraulic pump 1 is smaller than the value corresponding to the load pressure, that is, the flow amount is smaller than the flow amount required by the opening area of the directional control valve 5 for the methine opening. Become. As a result, the actuator 6 starts moving slowly.

In other words, the oil hole 45, the space 47, the port 46, and the third port 40 are tanks 4 when the spool 15 of the pressure reducing valve 3 moves halfway. 2 constitutes a bridge-off circuit. As described above, since the pressure in the second pressure chamber 11 is lower than the load pressure in the first pressure chamber 10, the spool 15 is pushed further to the right, and as shown in FIG. Take a balanced position in the vicinity.

As a result, the port 46 is cut off from the third port 40 and the above-mentioned bleed-off circuit is cut off, so that the pressure oil in the pump discharge passage 24 only flows through the second port 14. Will be supplied to Therefore, as in the conventional case, the pressure in the load pressure detection path 27 becomes equal to the load pressure, and the discharge amount of the variable hydraulic pump 1 becomes a value corresponding to the load pressure. The required flow rate is determined by the area of the main opening. As a result, the actuator 6 starts to operate at a predetermined speed after a certain time has elapsed after the start of the movement.

Because of this, the spool 23 of the directional control valve 5 is moved to the neutral position and the pressurized oil supply position for a short time (the time required for the spool 15 to move from the neutral position to the position that balances near the right end). (Shorter time) by alternately switching, the metering opening area of the directional control valve 5 is reduced, and the discharge amount of the variable hydraulic pump 1 is always smaller than the required flow amount. As a result, the actuator 6 can always be moved slowly, so that the inching operability is improved throughout the entire operation.

As described above, according to the first embodiment, when the spool 23 of the directional control valve 5 is moved from the neutral position to the pressure oil supply position to supply the pump discharge pressure oil to the actuator 6. Since the spool 15 of the pressure reducing valve section 3 slowly moves toward the first position due to the load pressure of the actuator 6, the pressure of the load pressure detecting path 27 decreases. The discharge amount of the variable displacement hydraulic pump 1 gradually increases, and the actuator 6 does not suddenly operate.

Also, when the spool 15 of the pressure reducing valve section 5 is at the intermediate position between the second position and the first position, a part of the pump discharge pressure oil flows out to the tank, and the pressure of the load pressure detection path 27 becomes the load pressure. And the discharge rate of the variable displacement hydraulic pump 1 becomes smaller than the value corresponding to the load pressure, and the supply flow rate to the actuator 6 is reduced by the directional control valve 5. When the spool 15 moves to the first position, the pressure in the load pressure detection path 27 becomes equal to the load pressure and the variable displacement hydraulic pump The discharge rate of the pump 1 is a value commensurate with the load pressure, and the flow rate supplied to the factory 6 is the required flow rate due to the area of the directional control valve 5 opening the mesh.

Therefore, when the direction control valve 5 is operated by a small amount to perform the inching operation on the actuator 6, the speed at which the actuator 6 starts moving becomes slower, so that a smooth inching operation can be performed. If it is moved to the position, the supply flow rate to the actuator 6 becomes the required flow rate due to the opening area of the directional control valve 5, and the actuator 6 can be operated at a predetermined speed.

In the above embodiment, the pressure compensating valve 4 and the directional control valve 5 are provided in one valve block, but may be provided in separate valve blocks. Next, a second embodiment of the present invention will be described with reference to FIGS. As shown in Fig. 6, the spool 23 of the directional control valve 5 is held at the neutral position by the left and right springs 50 and 51, and the right side by the pilot pressure oil of the left first pressure receiving chamber 52. To the first pressure oil supply position and move to the second pressure oil supply position by being pushed to the left by the pilot pressure oil in the right second pressure receiving chamber 53. ing. The amount of movement of the spool 23 to the first and second pressure oil supply positions (metering opening area) is determined by the amount of pilot pressure oil in the first and second pressure receiving chambers 52 and 53. It is proportional to pressure.

Hydraulic pilot valve 54 It has first and second pressure-reducing valve parts 56 and 57 for supplying pressure oil discharged from the hydraulic pump 55 to the first and second pressure-receiving chambers 52 and 53, respectively. The outlet port of the valve section 56 is connected to the first pressure receiving chamber 52 by the first pilot circuit 58, and the outlet port of the second pressure reducing valve section 57 is connected to the second pilot circuit 59. To the second pressure receiving chamber 5 3 It is connected.

The first and second pressure reducing valve sections 56 and 57 are held at a position for shutting off the inlet port and the outlet port when the operating lever 60 is in the neutral position Α. Is operated from the neutral position A in one direction (the direction of arrow a), the inlet port and the outlet port of the first pressure reducing valve section 56 communicate with each other, and the pilot port is connected to the first outlet circuit 58. Pressure oil is output. The pressure of the pilot pressure oil is proportional to the operation amount of the operation lever 60.

When the operating lever 60 is operated in the other direction (the direction of arrow b), pilot pressure oil having a pressure proportional to the operation amount is output to the first pilot circuit 59 as described above.

The relationship between the operation amount of the operation lever 60 of the hydraulic pilot valve 54 and the output pilot pressure is, for example, as shown in FIG.

In other words, the pilot pressure is P1 at the first intermediate manipulated variable L1, the pilot pressure is P2 at the second intermediate manipulated variable L2, and the pilot pressure is P2 at the third intermediate manipulated variable L3. Pilot pressure is P3 and pilot pressure is P4 at the maximum manipulated variable L4 (Pi <P2 <P3 <P4) o

When the operation lever 60 is operated from the neutral position A by a small amount, a dead zone may be provided so as not to output the pilot pressure.

On the other hand, the spool 23 of the directional control valve 5 takes the pressurized oil supply position when the pilot pressure becomes P1, and the mating opening area at that time is the smallest. Thereafter, when the pilot pressure sequentially increases to P 2 P 3, the meter-in area increases, and at the maximum pilot pressure P 4, the area of the mesh opening becomes maximum.

The load pressure detection path 27 is connected to a bleed-off circuit 61, and the bleed-off circuit 61 is provided with a load pressure bleed-off valve 62. is there. The load pressure blade-off valve 62 is switched between a first shut-off position E, an intermediate blade-off position F and a second shut-off position G, and is held at the first shut-off position E by a spring 63. When the pilot pressure supplied to the pilot pressure receiving portion 64 becomes P2, the intermediate blade-off position F is opposed to the spring 63 and the pilot pressure becomes P3. 2 Moved to blocking position G.

The pilot pressure receiving section 64 is connected to a high-pressure detection circuit 65, and the high-pressure detection circuit 65 is connected to first and second pilot valves 66, 67 via first and second check valves 66, 67. The cut circuits 58 and 59 are connected to a tank 69 via a throttle 68.

Next, the operation of the present embodiment will be described.

When the operating lever 60 of the hydraulic pilot valve 54 is in the neutral position A, the pilot pressure output from the hydraulic pilot valve 54 is zero. The spool 2 of the directional control valve 5 3 is a neutral position with the left and right springs 50 and 51.

Further, since the pressure of the high-pressure detection circuit 65 is zero and the pilot pressure of the pilot pressure receiving portion 64 is zero, the load pressure blade-off valve 62 is actuated by the spring 63 to act as a spring. 1Take cutoff position E. Accordingly, the blow-off circuit 61 is shut off, and the discharge amount of the variable hydraulic pump 1 becomes the set minimum discharge amount.

When the operating lever 60 of the hydraulic pilot valve 54 is operated in one direction (the direction of the arrow a) by the operating amount L1

Since the hydraulic pilot valve 54 outputs the pilot pressure P1 to the first and ^zero- outlet circuits 58, the spool 23 of the directional control valve 5 moves to the right and moves to the right. 1 Pressure oil supply position, with minimum mating opening area Become.

On the other hand, the pilot pressure P 1 is supplied from the high pressure detection circuit 65 to the pilot pressure receiving section 64, but the load pressure blade-off valve 62 is operated by the spring 63. And remains at the first shut-off position E. Therefore, since the blow-off circuit 61 remains shut off, the load pressure in the load pressure detection circuit 27 is supplied to the pump control directional control valve 26, and the discharge amount of the variable hydraulic pump 1 is reduced. Increases as you climb.

This operation is continued until the pilot pressure reaches P2 by operating the operation lever 60 to the stroke L2.

When the operating lever 60 of the hydraulic pilot valve 54 is operated in one direction by the stroke L2

The pilot pressure of the first pilot circuit 58 becomes P2, and the spool 23 of the directional control valve 5 moves further to the right to increase the area of the mating opening. The pilot pressure of the cut pressure receiving part 6 4 becomes P 2, the load pressure feed-off valve 62 takes the intermediate feed-off position F, and the feed-off circuit 61 turns the throttle 7 off. Connect to the tank via 0. As a result, a part of the load pressure of the load pressure detection circuit 27 flows out (bleed off) to the tank, and the load pressure supplied to the pump adjustment directional control valve 26 becomes the actual load. The pressure becomes lower than the pressure, and the discharge amount of the variable hydraulic pump 1 becomes smaller than the discharge amount corresponding to the actual load pressure.

In other words, the discharge amount of the variable hydraulic pump 1 is smaller than the required flow rate of the directional control valve 5 according to the mating opening area.

As a result, the flow rate supplied to the actuator 6 is reduced, so that the actuator 6 operates at a very low speed and the inching operability is improved. At this time, the spool constituting the pressure reducing valve section 3 of the pressure compensating valve 4 Since 15 moves slowly, the load pressure also rises slowly, and this operation, together with the aforementioned load pressure pre-off, makes the inching operability remarkable. Improve.

This operation is continuously performed by operating the operation lever 60 up to the operation amount L3 until the pilot pressure becomes P3.

When the operation lever 60 of the hydraulic pilot valve 54 is operated in one direction by the operation amount L3

The pilot pressure of the first pilot circuit 58 becomes P3, the spool 23 of the directional control valve 5 moves further rightward, and the area of the meteine opening further increases. As a result, the pilot pressure P 3 of the pilot pressure receiving portion 64 becomes the pilot pressure P 3, the load pressure blade-off valve 62 becomes the second shutoff position G, and the blade-off circuit 61 comes out of the tank. Will be shut off.

As a result, the load pressure of the load pressure detection circuit 27 becomes the actual load pressure, and the discharge amount of the variable hydraulic pump 1 becomes a discharge amount commensurate with the actual load pressure. The supply flow rate to the directional control valve 5 is the required flow rate according to the area of the main opening.

This operation is continuously performed by operating the operation lever 60 up to the maximum operation amount L4 until the pilot pressure becomes P4.

As described above, according to the operation amount of the operating lever 60 of the hydraulic pilot valve 54, the bleed-off valve 62 is set to the first / second shut-off position and the intermediate bleed-off position. Since the switching is performed, when the mating opening area of the directional control valve 5 is an intermediate size, a part of the load pressure of the load pressure detection circuit 27 is bleed off, and the discharge amount of the variable hydraulic pump 1 is reduced. The supply flow rate to the actuator 6 becomes smaller than the flow rate required by the meter-in opening area of the directional control valve 5, and the operation of the actuator 6 is Since there is no relation to the amount of movement of the spool 15 constituting the pressure reducing valve section 3 of the force compensating valve 4, the inching operability is excellent.

That is, in the first embodiment, a part of the load pressure is bled off by the moving amount of the spool 15 constituting the pressure reducing valve section 3 of the pressure compensating valve 4, and the hydraulic pilot valve is used. Even if the operation amount of the operation lever 54 is set between L2 and L3, the spool 15 moves with the passage of time and does not blow off part of the load pressure. Therefore, if the operating lever 60 is alternately operated between the neutral position A and the operating amounts L2 and L3 in a short time, the actuator 6 operates slowly, and the Operability improves o

However, when the operation lever 60 is held between the operation amounts L2 and L3 for a long time, the spool 15 does not move off as described above, and the variable hydraulic pump is not operated. The discharge amount of 1 becomes a discharge amount commensurate with the actual load pressure, and the factories 6 operate quickly and the inching operability decreases.

On the other hand, according to the second embodiment, when the operation lever 60 of the hydraulic pilot valve 54 is operated between the operation amounts L2 and L3, there is no relation to the movement amount of the spool 15. Since part of the load pressure can be blown off, the inching operability is improved.

As described above, according to the second embodiment, the methine opening area of the directional control valve 5 and the load pressure blow-off valve 62 are switched according to the magnitude of the operation command. However, if the size of the operation finger to be set for the inching operation is set to the middle size, the opening area of the mating valve becomes small, and the load pressure bleed-off valve 62 is in the pre-off position. Therefore, during the inching operation, the discharge amount of the variable displacement hydraulic pump 1 exceeds the required flow rate. After a while, the actuator 6 operates slowly and the inching operability is improved.

In the case of the second embodiment, the spool 15 constituting the pressure reducing valve portion 3 of the pressure compensating valve 4 does not move slowly, for example, a pressure chamber 31 is formed as shown in FIG. It is possible to use a general pressure that is pushed in the opening direction by the primary pressure and is pushed in the closing direction by the load pressure as shown in Fig. 9 so that the primary pressure matches the load pressure. A compensation valve may be used.

Next, as an application example of the second embodiment, when a plurality of directional control valves 5 are provided and pressure oil is supplied to a plurality of actuators 6, the load pressure ⁰ Lee Lock preparative examples supplying pie Lock preparative pressure pressure-receiving pressure section 6 4 with reference to FIG. 1 0 to 1 2 will be described.

As shown in Fig. 11, the valve bodies 71 of the directional control valves 5 are overlapped and connected so that each first tank port 21 and each second tank port 22 are adjacent to the valve body. The first tank port 21 and the second tank port 22 are communicated by the oil hole 73 of the block 72 connected to one valve body 71. Further, both ends of the spool 23 are protruded into the case 74 attached to both end surfaces of each valve body 71 so that the first and second pressure receiving chambers 52 are provided between the both end surfaces and the case 74. , 53, respectively.

As shown in FIG. 12, first and second oil holes 80 and 81 are formed near both ends in the longitudinal direction of the spool in each valve body 71, and the first oil holes 80 are respectively connected to the first pressure receiving holes 80. A first check valve 82, which communicates with the chamber 52, is provided in each case 74, and a second check, which communicates the second oil hole 81, with the second pressure receiving chamber 53, respectively. Valve 8 3 It is provided in the other case 74 respectively.

Each of the first oil holes 80 communicates with the adjacent valve body 71, and communicates with the oil hole 84 of the block 72, and each of the second oil holes 81 communicates with the adjacent valve body 71. and each communicating between communication with the oil hole 8 4 blocks 7 2, which first respective Ri by the oil hole 8 0 and the second oil hole 81 to _c is found to be communicated, block The oil hole 84 of 7 4 communicates with the tank 86 through the throttle 85.

In other words, the first and second check valves 82 and 83 correspond to the first and second check valves 66 and 67 in FIG. 6, and the restrictor 85 and the tank 86 correspond to the first and second check valves 66 and 67 in FIG. The diaphragm 68 and the tank 69 in FIG. 6 correspond to the oil hole 84 and the high-pressure detection circuit 65 in FIG.

The oil hole 84 of the block 72 is connected to the pilot pressure receiving portion 64 of the load pressure blow-off valve 62.

Next, the operation of this application example will be described.

When the operating pressure 60 of one hydraulic pilot valve 54 is operated to output the pilot pressure to the first and the ^0th pilot circuit 58, the pilot pressure is increased to the second level. 1 Supplied to the pressure receiving chamber 52, the spool 23 is pushed rightward to the first pressure oil supply position.

At the same time, the pilot pressure in the first pressure receiving chamber 52 flows into the first oil hole 80 through the first check valve 82, and further flows through the first oil hole 80. It flows into the oil hole 84 of the lock 72 and is supplied to the pilot pressure receiving portion 64 of the load pressure blade-off valve 62.

When the operating lever 60 of the hydraulic pilot valve 54 is returned to the neutral state from the state described above and the first pilot circuit 58 is communicated with the tank, the pressure in the first pressure receiving chamber 52 is reduced. And the spool 2 3 becomes the spring 5 1 To return to the neutral position, and at the same time, the pressure oil in the oil hole 84 of the block 72 flows out of the throttle 85 to the tank 86, and the pressure in the oil hole 84 decreases. Therefore, the pressure in the pilot pressure receiving portion 64 of the load pressure blow-off valve 62 also decreases.

The same operation as described above is performed also when the pilot pressure is output to the second pilot circuit 59.

With this configuration, one load pressure blow-off valve 62 may be provided for a plurality of directional control valves 5, and the first and second check valves 82, 83 are provided. This eliminates the need for a flexible body, and reduces costs, and eliminates the need to install the first and second check valves, making the entire system compact.

In the case of a directional control valve 5 that supplies pressure oil to the factory 6 that does not require inching, as shown in Fig. 13, the pressure oil introduction hole 75 of the body 74 or the valve body 71 The plug 77 can be press-fitted into the oil hole 76 that connects the first and second oil holes 80 and 81 to the first and second check valves 82 and 83, respectively.

Incidentally, the hydraulic Roh spool 2 3 of the directional control valve 5 in the second embodiment, ⁰ Lee Lock While switched pie Lock bets pressure from bets valve 5 4, the electric lever as shown in FIG. 1 4 The electromagnetic proportional switching valve 91 is switched by the current output from the device 90, and the pilot pressure is applied to the first and second pressure receiving chambers 52, 53 at both ends of the spool 23 of the directional control valve 5. May be supplied. Also, as shown in FIG. 15, the position of the spool 23 of the directional control valve 5 is switched by an electromagnetic proportional solenoid 92, and the load pressure blade-off valve 62 is moved to the electromagnetic proportional solenoid. The current is supplied from the electric lever device 90 by using the electromagnetic proportional solenoid.

Claims

It is also possible to supply to the solenoid proportional solenoid 93 of the load pressure blade-off valve 62 together with the supply to the solenoid 92. Note that 94 is a diode. In other words, if the directional control valve 5 has a mating opening area proportional to the size of the operation finger, and the load pressure blow-off valve 62 switches according to the magnitude of the operation command. good. Although the present invention has been described with reference to exemplary embodiments, various changes, omissions, and additions may be made to the disclosed embodiments without departing from the spirit and scope of the invention. That is obvious to those skilled in the art. Therefore, the present invention should not be construed as being limited to the above-described embodiments, but as encompassing the scope defined by the elements recited in the claims, and equivalents thereof. Must. The scope of the claims

1. A variable displacement hydraulic pump whose discharge is controlled by the load pressure in the load pressure detection path, a pressure compensating valve consisting of a check valve and a pressure reducing valve, and a pump discharge A directional control valve for supplying pressure oil, wherein the check valve portion communicates and shuts off between a pump discharge passage of the variable displacement hydraulic pump and a pump port of the directional control valve. Have a pool,

The pressure reducing valve section,

It is pushed toward the first position that connects the pump discharge path and the load pressure detection path by the load pressure of the actuator, and is pressed by a weak spring and the load pressure of the load pressure detection path. And a spool pressed toward a second position for shutting off the pump discharge path and the load pressure detection path and pressing a spool of the check valve portion in a closing direction. Moving slowly from the second position to the first position,

A pressurized oil supply having a bleed-off circuit that discharges part of the pressurized oil from the pump discharge passage to the tank at a position intermediate between the second position and the first position.

2. The pressure reducing valve portion communicates with the first pressure chamber, which receives the load pressure and pushes the spool toward the first position, via the damper throttle to the pump discharge path, and connects the spool with the first pressure chamber. A pressure chamber that pushes toward the second position, and a second pressure chamber that communicates with the load pressure detection path via a throttle to push the spool toward the second position, wherein the spool is in the second position. At this time, the pressure chamber is disconnected from the load pressure detection path, and when the spool is at an intermediate position between the second position and the first position, the pressure chamber is shut off. And a pressure chamber that communicates with the load pressure detection path when the spool is at the first position. Pressure oil supply device.

3. A variable displacement hydraulic pump whose discharge rate is controlled by the load pressure in the load pressure detection path;

A directional control valve that is switched from a neutral position to a pressure oil supply position by an operation finger to supply pump discharge pressure oil to the actuator overnight, and that a mating opening area is proportional to the operation finger;

A pressure compensation valve which is pushed in the opening direction by the pump discharge pressure and is pushed in the closing direction by the load pressure of the actuator to make the primary pressure correspond to the load pressure;

A blade-off circuit connected to the load pressure detection path;

It is provided in the bleed-off circuit, and when the size of the operation finger is an intermediate size, it is at the bleed-off position, and when the size of the operation finger is other than the middle, it is shut off. A pressure oil supply device consisting of a load pressure blow-off valve that is positioned.

4. The operation command is a pilot pressure output from the hydraulic pilot valve as a pressure proportional to the operation amount of the operation lever,

The directional control valve is switched from the neutral position to the pressurized oil supply position by the pipe port pressure to supply the pump discharge pressure oil over a short period of time, and the mating opening area of the pump is increased. The pressure oil supply device according to claim 3, wherein the pressure oil supply device is proportional to the pressure of the lot pressure.

5. The directional control valve has a spool fitted into the valve body and slidable between the neutral position and the pressure oil supply device by the spring and the pilot pressure in the pressure receiving chamber. Have been A plurality of the directional control valves are overlapped and connected to each other,

Oil holes connected between the valve bodies adjacent to the valve bodies, and check valves communicating the oil holes with the pressure receiving chambers are provided, and the oil holes are connected to the load pressure bleed-off valve pilot valves. The pressure oil supply device according to claim 4, wherein the pressure oil supply device is connected to a pressure receiving portion.

6. The pressure compensating valve is composed of a check valve and a pressure reducing valve,

The check valve section has a spool that communicates and shuts off a pump discharge path of a variable displacement hydraulic pump and a pump port of a directional control valve,

The pressure reducing valve section,

The pump pressure is pressed toward the first position that connects the pump discharge path and the load pressure detection path by the load pressure of the actuator, and the pump discharge path and the load pressure detection are performed by the weak spring and the load pressure of the load pressure detection path. A spool that is pressed toward a second position that blocks the passage between the first and second passages and that pushes the check valve spool in a closing direction, and the spool is moved from the second position to the first position. The pressure oil supply device according to any one of claims 3 to 5, characterized in that the pressure oil supply device moves slowly toward the pressure oil supply device.

7. The operating lever is an electric lever device, and the electromagnetic proportional switching valve is switched by the current output from the electric lever device to control the pilot pressure in the first and second pressure receiving chambers of the directional control valve. The pressure oil supply device according to claim 4, wherein the pressure oil supply device is configured to supply the pressure oil.

8. The operation command is an electric signal output from an electric lever device, and the position of the spool of the directional control valve is switched by an electromagnetic proportional solenoid, and the load pressure lead-off valve is switched to another position. The electromagnetic lever is used to switch the current, and the electric lever device supplies current to the electromagnetic proportional solenoid, and the load pressure lead-off valve 4. The pressure oil supply device according to claim 3, wherein the pressure oil is supplied to the electromagnetic proportional solenoid.